Merge branch 'adil-e1-master-patch-25467' into 'master'

Update project_level_variables.md to include an example of how to add a...

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/166071



Merged-by: Marcel Amirault <mamirault@gitlab.com>
Approved-by: Marcel Amirault <mamirault@gitlab.com>
Co-authored-by: Adil <adil.abdulkareem@outlook.com>